Re: Shared buffers, db transactions commited, and write IO on Solaris

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

Erik Jones <erik(at)myemma(dot)com> writes:
> We've recently made a couple changes to our system that have resulted  
> in a drastic increase in performance as well as some very confusing  
> changes to the database statistics, specifically  
> pg_stat_database.xact_commit.  Here's the details:

I'm kinda boggled too.  I can see how increasing shared buffers could
result in a drastic reduction in write rate, if the working set of your
queries fits in the new space but didn't fit in the old.  I have no idea
how that leads to a drop in number of transactions committed though.
It doesn't make sense that autovac would run less frequently, because
it's driven by number of tuples changed not number of disk writes; and
that could hardly account for a 10x drop anyway.

Did you by any chance take note of exactly which processes were
generating all the I/O or the CPU load?

			regards, tom lane